A micro total analysis system (“μTas”, also called a lab-on-a-chip system) integrates microfluidics components with microelectromechanical systems (MEMS) into a single miniaturized device. The micro total analysis system can be used to perform chemical and biological analyses, such as capillary electrophoresis (CE), flow cytometry, liquid chromatography (LC), and mass spectroscopy (MS). The micro total analysis system can also be used to synthesize chemicals and drugs, and carry out clinical analyses. The micro total analysis system includes microfluidic devices that are used to manipulate and analyze fluid samples. Examples of microfluidic devices include microchannels, microvalves, micropumps, and micromixers. Because the components of the μ Tas are integrated together, only small amounts of fluid and sample are required for the analyses. This improves system performance and reduces sample, reagent, and analysis costs.